This invention relates to slide calculators, and more specifically, to a calculator for determining factors relating to lighting as used in photography for correctly exposing film. Since electronic flash is the most popular form of artificial light used in photography, the word flash is used herein to mean any artificial light source. Light is one of many necessary factors involved in photography, annd studio photography requires artificial light. Some of the factors affecting the amount and quality of light striking the film in a camera are lens f-stop, exposure factors of filters over the lens, light-ratio, exposure factors of filters over the flash, size of the flashes, power setting of the flashes, the angle of the main-flash in relation to the camera-subject line and the distance of the flashes from the subject.